screen unlocked after wakeup for few seconds

After wakeup from suspend mode the screen shows the last state before putting the computer to sleep. After a few (approx. 1 to 5) seconds the screen becomes locked.
So, everything, I've done before closing the laptop (then it falls asleep), is exposed to some nosy people.

This might be a privacy issue for others too.

Is there a way to force the computer into the lock- or the logon screen immediately (e.g. before switching to hibernate state) in a way, the desktop contents are hidden?

Could it be bug?

edit: It's a HP elitebook 2760p runing the Wily Werewolf release.